This invention relates to pressure switches for use in automobiles, tractors and other heavy equipment and the like to provide an electrical signal or output in response to the occurence of selected pressures in the equipment during equipment operation. The invention relates more particularly to pressure switches having improved compactness, simplicity and reliability to make them more suitable for widespread use in automobiles.
Conventional pressure switches include contact means which are movable between open and closed circuit positions. The switches usually have a domed disc spring arranged to move from one dished configuration to an inverted configuration with snap action for moving the contacts sharply between those two circuit positions when sufficient force is applied to the disc. A diaphragm is exposed to fluid pressures in a zone to be monitored and is arranged to apply such a force to the disc when a selected level of pressure is applied to the diaphragm. In one commonly used pressure switch of that type, the contact means are biased to a closed circuit position. The disc is rested on its periphery or rim to extend over the contacts with the domed or convex side of the disc facing the diaphragm. A motion transfer member is located between the diaphragm and disc and has an annular portion which rests against a selected diameter portion of the convex side of the disc when the disc is in its original configuration. The member moves in response to the application of selected pressure to the diaphragm to apply force to that selected diameter of the disc to snap the disc to its inverted dished configuration. As the disc moves to that inverted configuration, it engages and moves the contact means to open circuit position against the normal contact bias. In that arrangement, it is found that some difficulty is encountered in incorporating the contacts in the switch in a compact and inexpensive way while also assuring that there will be adequate spacing between switch components of opposite polarity after the switch has opened in response to the occurrence of an overload pressure or the like. The pressure responsive devices also tend to be held in closed circuit position with less force than would be desired in many applications involving significant equipment vibration.
It is an object of this invention to provide a novel and improved pressure responsive device having improved compactness, reliability and simplicity for widespread use in automobiles.